1. Field of the Invention
The present invention relates to a locking mechanism of a webbing retractor which has a winding shaft around which a webbing is wound in the form of layers. The locking mechanism is capable to prevent from rotating the winding shaft at excessive movement more than a predetermined amount of acceleration in a horizontal direction of a vehicle.
2. Description of the Related Art
A seat belt apparatus for a vehicle is provided with a webbing retractor which accommodates a webbing for restricting movement of a seat occupant by resiliently winding in a laminating condition the webbing around a winding shaft to which one end of the webbing is fixed. The seat occupant draws the webbing out of this webbing retractor when he puts it on.
The webbing retractor has a locking mechanism for preventing the rotation of the winding shaft when the running speed of the vehicle rapidly drops to prevent the unwinding of the webbing and to thereby restrict the movement of the seat occupant.
FIG. 6 shows a conventional locking mechanism a type described above. In this locking mechanism, rotation of the winding shaft 10 is prevented when ratchet wheels 12 which are fixedly mounted on the winding shaft 10 are engaged with a pawl 14. A pendulum 16 is connected to this pawl 14 near a laminated portion 15 of the webbing. The pawl 14 is engaged with the ratchet wheels 12 by the swing of the pendulum 16. The pendulum 16 swings when a predetermined amount of acceleration acts in a horizontal direction of a vehicle or in a widthwise direction shown in FIG. 6, that is, when the running speed of the vehicle rapidly drops, and thereby causes the pawl 14 to be meshed with the ratchet wheels 12 so as to prevent from rotating the winding shaft 10.
However, in this locking mechanism, the pendulum 16 requires a long rod 16A, and this makes the locking mechanism long in a vertical direction (in a lengthwise direction shown in FIG. 6), which in turn makes a resultant webbing retractor elongated in the vertical direction.